Ive had my R now for 30k+miles and have used it for everything from 2.5wks touring around england, couple of weekend ralleys (1 of which was in a snow covered feb), 20mile commute for 3 university years, about 2weeks worth all in of off roading here there and everywhere and the usual scratching about, sunday rides etc etc

Im 6ft4 and on the heavy side of 14st and found it to be a really good compromise of a bike that can be tweeked and changed with many cheap little items to make it into so many different types of bikes. For off roading a got a £50 bash plate, £30 rear raiser links and the usual off road tyres and the bike was ready (ok no motoX bike but what ever ive taken it on ive only once had to back out and even then just took a different route down). It is surprisingly capable of doing off roading on the standard road basis tyres but once it gets muddy or wet you need proper knobblies on but the bike can still show up a not so well ridden off road bike.

Ive always had the yamaha tall black screen which allows me to cruise at 70mph all day (wind just hits on the top of the shoudlers/neck) and my bum has got use to the seat. I did make my own home made air hawk for the longer motorway miles but ended up loosing to much feeling from the bike.

The R and the Tenere are not really that much different in terms of usable parts, ok the frame, swing arm and forks arent the same but most of the things like seals, filters, bearings are the same.

As for the BMW never ridden one but ive read alot of stories about them, some good, alot bad. Sat on one in a show room and to tell the truth the bike was soo small i didnt even try and put my feet on the pegs

Get logged on to the xt660.com forum and there plenty on there about the XT660X/R and Z